Lapatinib (a dual inhibitor of epidermal growth factor receptor [EGFR] tyrosine kinase 1 and 2 [HER2]) in combination with capecitabine has been shown to prolong progression-free survival (PFS), and this combination is indicated for the treatment of patients with advanced or metastatic HER2-positive breast cancer who have received prior therapy including an anthracycline, a taxane, and trastuzumab [18]. This evidence concerns the gene ERBB2 and breast cancer.